Since the power system was varying from DC 750 to 1 250 V, a power conversion system was designed to solve the power supply to a 660 V AC three-phase pump motor. In the system, a two-level frequency conversion inverter was adopted which was based on space vector pulse width modulation and V/F control. During the research, a key technology was developed which focuses on the DC input, varying in a wide range, converting into the AC output and the solution was proposed. This solution was verified by load experiments and proved to be effective and reliable.